Asfotase Alfa: uses, dosing, side effects & brands
Asfotase Alfa is a tissue-nonspecific alkaline phosphatase sold in the U.S. under one brand, for hypophosphatasia. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Drug class
- Tissue-Nonspecific Alkaline Phosphatase
- Treats
- Hypophosphatasia
- Available as
- Solution
- Sold as
- Strensiq
- Prescription?
- Prescription only
- Generic available?
- Not in our catalog
- Boxed warning
- Boxed warning
How asfotase alfa is dosed
From the FDA label for Strensiq (application BLA125513). Other asfotase alfa products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
Perinatal/Infantile-Onset HPP ( 2.2 ) Recommended dosage regimen is 2 mg/kg administered subcutaneously three times per week, or 1 mg/kg administered six times per week. Injection site reactions may limit the tolerability of the six times per week regimen. The dose may be increased to 3 mg/kg three times per week for insufficient efficacy. Juvenile-Onset HPP ( 2.3 ) Recommended dosage regimen is 2 mg/kg administered subcutaneously three times per week, or 1 mg/kg administered six times per week. Injection site reactions may limit the tolerability of the six times per week regimen. Preparation and Weight-Based Dosing ( 2.4 ): Caution: Do not use the 80 mg/0.8 mL vial in pediatric patients weighing less than 40 kg because the systemic asfotase alfa exposure achieved with the 80 mg/0.8 mL vial (higher concentration) is lower than that achieved with the other strength vials (lower concentration). A lower exposure may not be adequate for this subgroup of patients. See full prescribing information for tables of weight-based dosing by treatment regimen. Administration ( 2.5 ): For subcutaneous injection only. Rotate injection sites. Do not administer to areas that are reddened, inflamed or swollen. 2.1 Recommendations Prior to STRENSIQ Treatment Initiate STRENSIQ under the supervision of a healthcare provider with appropriate medical monitoring and support measures [see Warnings and…
Asfotase Alfa side effects
The following adverse reactions are described below and elsewhere in the labeling: Hypersensitivity Reactions [see Warnings and Precautions (5.1) ] Lipodystrophy [see Warnings and Precautions (5.2) ] Ectopic Calcifications [see Warnings and Precautions (5.3) ] Possible Immune-Mediated Clinical Effects [see Warnings and Precautions (5.4) ] Most common adverse reactions (≥ 10%) are injection site reactions, lipodystrophy, ectopic calcifications and hypersensitivity reactions. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Alexion Pharmaceuticals, Inc. at 1-844-259-6783 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The data described below reflect exposure to STRENSIQ in 99 patients with perinatal/infantile- or juvenile onset HPP (age 1 day to 58 years) treated with STRENSIQ, most for more than 2 years (range 1 day to 312 weeks [78 months]): 51 patients received at least 96 weeks (24 months) of treatment and 39 patients received 168 weeks (42 months) or more of treatment [see Clinical Studies (14) ] . Common Adverse Reactions Overall, the most common adverse reactions reported…
Who shouldn’t take asfotase alfa
None. None. ( 4 )
Asfotase Alfa drug interactions
Drug Interference with Laboratory Tests: Alkaline Phosphatase (ALP) is used as a detection reagent in many laboratory tests and the presence of asfotase alfa in clinical laboratory samples could result in erroneous test results. Inform laboratory personnel and discuss use of an alternative testing platform for patients on treatment. ( 7.1 ) Serum Alkaline Phosphatase : Serum ALP measurements are expected to be elevated during treatment and may be unreliable for clinical decision making. ( 7.1 ) 7.1 Drug Interference with Laboratory Tests Laboratory Tests Utilizing Alkaline Phosphatase as a Detection Reagent Studies have shown that there is analytical interference between asfotase alfa and laboratory tests that utilize an alkaline phosphatase (ALP)-conjugated test system, rendering erroneous test results in patients treated with STRENSIQ. ALP-conjugated test systems are utilized to measure substances such as hormones, bacterial antigens and antibodies. Therefore, it is recommended that laboratory assays which do not have ALP-conjugate technology be used when testing samples from patients who are receiving STRENSIQ. To avoid erroneous test results for patients treated with STRENSIQ, inform laboratory personnel that the patient is being treated with STRENSIQ and discuss the use of a testing platform which does not utilize an ALP-conjugated test system. Serum Alkaline Phosphatase High serum ALP measurements detected through clinical laboratory testing are expected in patients receiving STRENSIQ and reflect circulating concentrations of asfotase alfa . Do not rely on serum ALP measurements for clinical decision making in patients treated with STRENSIQ.
Every asfotase alfa product we track (1)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
Only one: Strensiq.
What people report to the FDA about asfotase alfa
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 49 reports naming asfotase alfa, and the FDA flagged 55% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- blood alkaline phosphatase increased8 reports
- injection site erythema5 reports
- injection site pain5 reports
- anaphylactic reaction4 reports
- arthralgia4 reports
- injection site swelling4 reports
- mobility decreased4 reports
- injection site reaction3 reports
Read these as a signal, not a rate. A report does not mean asfotase alfa caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved July 25, 2026.
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Frequently asked questions
What is asfotase alfa?
Strensiq (Asfotase Alfa) is a tissue-nonspecific alkaline phosphatase used to treat Hypophosphatasia.
What kind of drug is asfotase alfa?
The FDA classifies asfotase alfa as a tissue-nonspecific alkaline phosphatase. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.
Can you take asfotase alfa with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run asfotase alfa against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What forms does asfotase alfa come in?
Across the brands we track, asfotase alfa is currently marketed as solution, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic asfotase alfa?
We do not currently list a generic-labelled asfotase alfa product. That does not always mean none exists — it means none appears under a generic name in the FDA data we track. Ask your pharmacist.
Cite this page
- APA
- pharmaranks. (2026, July 24). Asfotase Alfa: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/asfotase-alfa
- MLA
- “Asfotase Alfa: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/asfotase-alfa.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for asfotase alfa on DailyMed (NIH) ↗ — including its boxed warning in full.